Curved windshield and wiper



- R. O DOSS CURVED WINDSHIELD AND WIPER June 23, 1953 4 Sheets-Sheet 1 Filed Oct. 1, 1948 June 23, 1953 Filed 001;. l, 1948 I CURVED WINDSHIELD AND WIPER 4 Sheets-Sheet 2 Bu W 8 I (I iiiii eggs June 23, 1953 Filed Oct. 1. 1948 v R. o. DOSS 2,642,615

CURVED WINDSHIELD AND WIPER 4 Sheets-Sheet '3 f z a a June 23, 1953 R. o. DOSS 2,642,615

CURVED WINDSHIELD AND WIPER Filed Oct. 1, 1948 4 Sheei-Sheet 4 Patented June 23, 1953 CURVED WINDSHIELD AND WIPER Raymond 0. Doss, Birmingham,

to General Motors Corporation,

Mich., assignor Detroit, Mich.,

a corporation of Delaware Application October 1, 1948, Serial N 01 52,308

3 Claims.

This invention relates to a windshield wiper for a curved windshield, and more particularly to the location of a windshield wiper and its drive shaft axis with respect to a curved Windshield.

The object of this invention is to locate the drive shaft axis for the wiper arm mechanism with respect to a curved windshield at the proper angle to obtain the minimum variation in the angle between the drive shaft axis and the blade arm, in order to minimize the pressure variations between the wiper blade and the curved windshield as the blade traverses the windshield.

Another object is to mount the drive shaft for the wiper arm perpendicular to a plane having the least variation from the surface curve of the wiper area of the windshield or the space curve of the mid-portion of the wiper as it traverses the curved windshield.

Another object is to provide a graphical method of determining the proper relation of the wind shield wiper drive shaft axis to the curved windshield in order to maintain a substantially uniform blade pressure as the blade traverses the wiped area of the windshield.

Another object is to locate a windshield wiper drive shaft axis with respect to a curved windshield, so that the wiper pressure increases as the blade approaches the end of the stroke, and thus aids in retarding the blade and decreases as the blade leaves the end of the stroke to aid in accelerating the blade to normal speed.

The windshield wipers now employed on fiat Windshields generally consist of a stiff blade, an arm and a drive shaft. The drive shaft is mounted adjacent and perpendicular to the windshield. One end of the wiper arm is transversely pivoted to the wiper blade. The other end of the arm is rotatively fixed to the drive shaft to reciprocate the blade and wiper arm transversely pivoted to the drive shaft to allow adjustment toward and away from the windshield, and to allow for variation in the distance between the windshield and the end of the drive shaft. A spring is provided in the transverse pivot between the arm and shaft to maintain the blade pressure 'on the windshield. When this blade is employed on a fiat windshield the angle between the arm and shaft will remain constant. Thus the blade pressure on the windshield will be constant. With the constant pressure and therefore load on the wiper motor, the normal reciprocating movement will not be changed.

This type of wiper has been adapted for use on curved Windshields by several methods. One method, employing a flexible wiper blade, is satisfactory for Windshields with a small general curvature. However, when the windshield has a more pronounced curve, the angle between the wiper arm and the shaft has a larger variation in order to maintain the end of the arm in contact with the windshield. The variation of this angle changes the spring tension, and thus the load on the wiper motor to cause the wiper blade to move at an irregular speed as it traverses the windshield.

Other methods have been proposed in which the windshield drive shaft is positioned obliquely with respect to the vertical elements of the curved windshield. This arrangement will enable a windshield wiper blade to traverse a curved surface such as a cone, but will not provide a, solution for use with irregular curved surfaces.

The present trend in automotive styling has produced a curved windshield. Each section or half of the windshield has a curve with a substantially fiat portion near the center of the car and a sharply curved portion near the side of the car, as shown in the drawings. The drive shaft should not be located below the flat portion of the curved windshield near the center of the car. With the drive shaft in this location the wiper blade will move through about a quarter turn from a vertical position near the center of the car to a horizontal position near the side of the car. In the horizontal position the blade will lie along the axis of maximum curvature of the windshield. Proper cleaning could be obtained only if the blade could flex or bend to conform to the most sharply curved portion of the Windshield.

Since the best results are obtained with the least bending of the wiper blade, the drive shaft axis is located in accordance with the present invention near the side of the car, so that the wiper blade will lie along the axis of the curve in the region of the least curvature Thus the wiper blade is substantially horizontal as it traverses the flat portion of the windshield curve, and is nearer vertical and thus substantially parallel to the substantially straight vertical elements as it traverses the sharply curved portion of the windshield. However, when the drive shaft is located below the sharply curved portion of v the wind-shield, the angular relation between the shaft and the windshield is critical. Slight variations in this angular relation will produce large variations in the angle between the wiper arm and shaft during each cycle of oscillation,

the right side view *3 of Figure the body profile drawings.

inch, etc,

' stemmed. The s A o ftheelements I'B indicates that this windshield and thus prevent proper wiper operation. The correct angular relation between the wiper shaft and the windshield, when determined in accordance with this invention, will minimize the angular variation between the wiper arm and shaft.

. In the drawings:

Figure 1 shows the body design profile views of the windshield portion "of an automobile and the geometric solution for determinin'g the position of the wiper shaft axis.

Figure 2 is an enlargement of the left front windshield profile view 2 of Figure -1 into a right front windshield profile view.

Figure 3 is an enlargement of the left side windshield profile view 3 of- Figure-1.

Figure 4 is an enlargement of the auxiliary view 4 taken on the sectionof Figure 3 on the line 44.

Figure 5 is a transverse section of Figure 4-"on the line 55 showing one trial section plane *BB -B'B.

Figure 6 is a vertical-sectionof Figure 5 on the trial pla'ne line BB -6B.

Figure '7 is an end view or'cross section of Figurefi.

'Figure 8 is a fragmentary enlargement of a portion of Figure lshow'ing the final determinatio'n'of the wiper shaft axis.

In the drawing, Figure 1 shows the complete 'drawing' of the curved windshield profile and the geometric solution employed to determine the correct angular position of the wiper shaft axis. When the wiper shaft axis is located in accordance with this invention a conventional windshield wiper having "a'drive shaft oscillated by a motor, a wiper arm pivoted to 'theend of the drive "shaft, and a spring "connected between the shaftand armto hold the blade in contact with the windshield, may be used on a'curve'd windshield. Examples or suitable windshield wiper constructions are shown in United States Patents 1,946;073 to Horton et a1. and 2,027,862 to Anderson et "al.

The windshield profile in the 'car position'as shown in the 'left front view 2 of Figure 1 and 2 is taken' from These views show the curvature of "the windshield profile 9 and adjacent 'body surfaces, the windshield outline or frame H, the roof line 12', the 'door frame line 13 and the hood opening line 14. The "coordinate planes employed to locate the curves and as reference planes to obtain dimensions have been retained in the views because they aid the visual representation 'andexplanation of the geometric solution. In the front view 2 of Figure 1 the vertical coordinate'planes 16 extending lengthwise of the car appear 'as-straight lines. From thece'ntral coordinate plane orcent'e'r line thecoordinate planes are'dimensionally located and indicated asthe 5-inch, stations with regard to the center plane. The horizontal coordinateplanes I! are dimensioned from the ground and thus in these 'viewsfare dimensionally indicated as 40-inch, 45 mm, etc. stations. The horizontal coordinates H extend through the -front view 2 of Figure 1. The intersection of the 'vertical' coordinate planes I 6 with the windshield profile B locateS 'the eleinen't's F8 "of the windshield shown in the side View 3. The elements ['8 are 'a'inrsmhauy numbness, 5, etc. to correspond to the vertical' coordinate planes in which they tr'a'ight and parallel relation war to the elements H3 in view 3.

measured-in side view 3 and laid ofi profile has no relation as shown in the front view 2, an auxiliary view l, which is a section of view 3 on the section line 44, is constructed on Work line The work line W'LA is drawn perpendic- The elements iscrview laredrawn perpendicular to the work lineWLil with the same spacing along the work line as the coordinate planes of front view 2. The distances from the work line WL i to the windshield frame H along each element l8 are along the corresponding element in'auxiliary view 4 to-determine the windshield frame outline H in auxiliary view 4. Thisview 4 is a projection on' an auxiliary plane through section line i-4,and perpendicular tothe central coordinateplan'e 0.

When the windsh-ieldprofile -9 and outline H is determined and defined, the position of the wiper arm pivot and the 'arm' and blade length may be selected to" achieve the best wiped; area. This may be done in the drawing-in view 4;,but because of the numerous factors involved including the personal characteristics of drivers, it has been found that the wipedareaior best vision should be determined by actua-l experimentation on amodel of the car. When the wiped area is determined on a'model, the blade and arm. lengths are-noted for design purposes and the arm pivot point '25 -is'-markedon the body, and the "path curve 2"! traversedby the end of the wiper arm is mark'ed'on' the windshield of the model car. The path curve 21 and the pivot point 26' are then transferred tO'jthB drawing. The curve 21 and pivot -point -26-may be transferred to views "2 and- 3 of Figure -1'by measuring the vertical and horizontal distances from, the coordinate reference planes. 'However, it is'easiert-o-transfer the curve 2| directly to view'4. The elements [B and work line W114 are marked on the modelcar and measurements The 'pivot point -26-may be located xiliary view '4 by measuring coordinates from the worlr line and an element "on the car =andtraiisierring these dimensions to view '4. 'T-h'n the curve 21 andpiVOt-point-Z'B may be projected to the side view 3 and front view 2.

Since the windshield profile 9 is curved, the

wiper arm path curve 26 does not appear as a true circular'arc in these views.

'In order to locate the optimum position of the windshield wiper axis in relation to the windshield, an optimum. plane which has the least variation 'from' the wiper :path curve must be determined.

It has beenfound that thefoptiinum plane rnay be located, by a geometric ---solution which will show-'the deviatmn -or variation of the wiper p'ath curve from a-series of trial'pl'anes. The 'solution'i-s based on the auxiliary viev'vd which "shows the windshield profile 9, curve 2| and the true length of the elements It. A transverse' section' S is ma'de of the windshield profile and curve 2|. If the windshield and the profile are the same, the profile curve -3| in view 5 is used in the remainder of the to the thickness of the moulding. In the normal design the profile curve 3| and the front face of the windshield 32 will have substantially the same curvature. Thus the points 22 and 23 of curve 2| may be projected on the windshield face 32 without significant error.

Using the transverse section of curve 2| shown in view 5 of Figure 1, a trial plane 6A is passed through the curve. The location of trial plane 6A is empirically selected to approximate the curve 2| in view 5.v Using trial plane 6A as a section plane the vertical sectional view 6 of Figure 1, which includes path curve 2| A, is constructed on the work line 6'A shown as a dotted line for clarity. In constructing the end. view of Figure 1 of the vertical section of the path curve it is preferable to have a balanced curve. In order to have a balanced curve the work line 'I'A is drawn through the end points 22 and 23 of curve 2|A. The end sectional view of Figure 1 is taken on thesection plane 7A which is perpendicular to work line 1A. The section plane 1A also represents the trial plane 6A in end sectional view 1. Thus the wiper path curve 2|A in view shows the a transverse or lateral variation of curve 2| from trial plane 6A. This curve shows a rather thick middle section and thus indicates a large variation.

Then a second trial plane 6B is selected and the similar curves 2|B and 2|B are drawn. Since the curve 2|B is not as thick as curve ZIA the change of the trial plane from GA to 6B is in the proper direction.

Selecting a third trial plane 60 rotated further in the same direction, the curve 2| C is obtained in the same manner. It will be noted that curve 2|B is thinner than either 2|A or 2|C. The curve 2|A is wider at the center, while curve 2|C is wider at the end. Selecting curve 2|B, which is the thinnest, the optimum plane 36 is drawn on the center line of this curve. Thus the optimum plane 36 is the mean plane of the thinnest variation curve. By positioning the windshield wiper axis 31 perpendicular to the optimum plane 36 the least variation between a straight wiper blade path and the true path over the curved windshield 32 is obtained.

In order to clearly show the relationship of the trial curves 2|A, 2|B and 2|C a portion of view 6 and View of Figure 1 has been enlarged to show the relative size of these curves in Figure 8. The trial plane 63 produces the thinnest trial curve 2|B. Since rotation of the trial curve in either direction to 6A or 6C produces a thicker trial curve 2| 'A or 2| '0, the trial plane 6B indicates the optimum trial plane. The optimum plane 36 drawn as a center line of curve 2|B intersects the section plane 13 on the line 4| or work line 'I'B connecting the end points 22 and 23 of the path curve 2|. The optimum wiper shaft axis 31 is drawn perpendicular to the optimum plane 36, and thus has a nonintersecting perpendicular relation with the line 4| The wiper shaft fitting 46 is shown in dotted lines in this view to illustrate its relative position to the optimum plane.

In order to clearly show all the details of this geometric solution employed to determine the optimum plane for the proper angularposition of the wiper drive shaft, the views 2 to of Figure 1 have been enlarged to show the details of the solution for the optimum trial curve 2|B. The car position views 2 and 3 are shown enlarged in Figures 2 and 3 with the right front view 2 reversed to show the left front windshield .in Figure 2, which was considered the more conventional companion view to the left side view in Figure 3. The auxiliary view 4 is shown enlarged to the same scale as Figures 2 and 3 in Figure 4. The geometric solution is based on Figure 4, and involves the selection of the trial planes and the sections shown in Figures 5, 6 and 7.

Referring to Figure 4, the auxiliary view of the windshield profile 9 shows the elements IS, the work line WL4, the wiper arm path curve 2| and arm pivot point 26 as determined above. The position of the wiper arm in the parked position is also shown in the dot-and-dash line. In finding the wiper axis position the sectional view Figure 5 of the windshield profile 9 is made on a plane through the work line WL4 or section line 5-5 and perpendicular to the elements I8. Figure 5 is constructed on the work line WL5, which is parallel to the work line WL4. The measurements are taken in Figure 3 from the element 0 along the work line WL4 to each element and laid off perpendicular to work line WL5 along the corresponding element to determine the points of the section curve 3| of the Windshield profile 9. The pivot point 26 is located with respect to the section curve by projecting parallel to the elements of Figure 4, and located above work line 'WL5 the same distance the pivot point 26 is located in Figure 3 from the element 0.

In building the car the windshield must be located inside the profile lines by the thickness of the windshield frame or moulding. Thus the front face 32 of the windshield is located a uniform distance inside of the profile section 3|. Since the windshield and profile section curves are almost exactly alike, the wiper arm length and the arm path curve 26 on the profile surface 9 will be practically the same as for the windshield surface 3|. If the curvature or the thickness of the windshield moulding introduced a perceptable error, it would be necessary to employ the windshield glass profile curves in Figures 2 and 3. However, in View of the fact that these curves are not ordinarily drawn in practice and the error involved is negligible, the body profile curves are here used.

The points 22 and 23 are located on the windshield section 32, Figure 5, by projecting from points 22 and 23 in Figure 4 parallel to the elements. A trial plane 63 is passed through the section 32 parallel to the elements. The selected location of the first plane can only be based on experience. In general, it should be close to the points 22 and 23 as shown in the drawing. For this description the trial plane 63 that gave the optimum plane has been used in order to show the transfer of the wiper shaft axis from the solution to the car position, Figures 2 and 3.

Figure 6 is a section of path curve 2| taken onthe trial plane 6B of Figure 5 and constructed on work line 6'B which is parallel to trial plane 63. The element lines are drawn from the points on the windshield section representing the elements or the intersection of the element planes and the windshield section 32 perpendicular to the work line 6'B or trial plane 6B. The distances along the elements from work line WL4 to plane 713 whichis perpendicular the point accuracy, 'threepoin'ts on parallel to the cur /e 21 are then laid ofi'along therespective elements from work line BBto give the points of curve 2113 in Figure 6. The points Hand 23 of Figure 6 arenow connected to produce work lines 1'13.

The trial curve ZI B shown in Figure 7 is a section of Curve 2133 of Figure 6 on the section to work line PB. The curve 2 l "B or Figure 7 is plotted by projecting-the points from Figure 6 parallel to the work line 1'13, and locating the points a perpendicular distance from section plane 1B equal to the'perpendicular distance from the trial plane 6B to the windshield section 32 or curve 2|, which is along the projected element lines of curve MB in Figure 6.

Since the trial curve 2I'B of Figure 7 is the narrowest'curve obtainable with this windshield and-path curve 21 the optimum plane 36 is drawn through the center of the curve 2IB of Figure 7. The wiper drive shaft axis 31 is located perpendicular to the optimum plane 36. However, before the shaft axis 31 can be located, the pivot point 26 must be located with respect to the trial curve Z'IB. The wiper arm pivot point 26 having been determined on the model car and located in the auxiliary view and car position views 2 and 3, is projected parallel to the elements of the auxiliary Figure 4 and located in Figure 5 above work line WL5 the distance it is from element in the side view, Figure 3. With 26 located in relation to section 32 in Figure 5, it is projected to Figure 6 on a perpendicular to trial plane 6313 and located'from work line t -B the same distance that point 26 is from work line V /L4 in Figure 4. For -usein the solution to be explained later a construction line 42 is drawn from point 26 perpendicular to line 4-1 or 'l'B which connects the end points '22 and 23 of curve -2iB in Figure 6. The point 2-6 a is then projected to Figure? parallel 'to work line VB and located a perpendicular distance from section plane 118 as point 26 is from trial plane 63in Figure 5.

From the point 26 thus located with relation to curve 2! "B-of Figure '1 aperpendicul'ar is dropped to the optimum plane 36 to determine the wiper shaft axis 31. in order to project this line into thecar position views and to have a check on the the axis are used. The point 26 has been located. The point 21 is at the intersection of the axis and the-section plane TB, and point 28 at the axis 'and the optimum plane 36. The points 21 and-i8 located with respect to curve ZE B of Figure 7 are projected work line lB to the construction lined as 21 and 28 in relation to curve 2TB of Figure 6. The points are then projected parallel tothe elements of curve 2H3 of Figure 6 or'perpendicular to trial'plane 6B, and located as points 2 and 28 with regard to the trial plane BB the same distance therefrom as from section plane TB. The'point 43 on work line VB is projected "parallel to the elements of curve "21B of Figure '6 to the trial plane 613 of the section curve 32 in Figure5. The points 2? and 28 are projected on the auxiliary view'parallel to the elements and "located from work line WM the same distance'as they are from work line 6B, Figure 6. The points 26,21 and 28 will be located in the side view, Figure 3, the same'distan'ce from work line WL4 as in the auxiliary view and the same distance from element 0 as from work line WL in Figure 5, and-in the front'view'the same'distan'ce from the-horizontal coordinator as in the side 'view and front and side views in carposition the necessary measurements can be made to locate the wiper axis on the car.

Thus in accordance with the invention the position of the wiper aXis for an irregularly curved windshield may be determined to produce aminimum variation between the normal wiper path and the path on the windshield surface.

The position of the windshield wiper axis may also be located to produce a corrective variation in the pressure between the wiper and windshield to increase or decrease the load on the wiper motor over certain portions of the wiper path. When reciprocating motors, such as the vane type vacuum motors are used to drive a windshield wiper on curved glass, it is advantageous to provide additional load as the blade approaches both ends of the path and to decrease this load as the blade leaves the end of the path. This may be done by making the external angle between the wiper axis 31 and the optimum plane 36 somewhat larger than as shown in Figure '7. An increase of from 1 to 5 degrees is normally sufficient to provide the required variation in wiper blade pressure. Thus the drive shaft or wiper shaft axis 31 is disposed with respect to the optimum plane 38 to subtend a horizontal angle of 90 and a vertical exterior angle on the windshield side or toward the windshield of 90 to degrees. With the angle larger than 90 the wiper pressure will increase as the blade approaches each end of the stroke and decreasea's the blade leaves each end of the stroke. Thus the variation in pressure on the wiper blade will assist the deceleration and acceleration that occurs at the end of each stroke of the reciprocating wiper blade.

The invention though illustrated by the above specific embodiments is subject to modification 'bythose skilled in the art which falls within the scope of'the appended claims.

I claim:

I. The combination with an irregularly curved windshield having a convex outer surface, of a windshield wiper assembly having a drive shaft "axis and a wiper arm, said Wiperarm having an end describing a non-planar path curve onsaid ascompared to other planes so intersecting said curve.

2. The combination withan irregularly curved windshield havin'g a convex 'outer surface, of a windshield wiper assembly having a drive shaft axis and'a wiper arm, sai'dwiper arm having an end de'scribing va non-planar path curve on said windshield during the oscillation of said arm about said axis, said axis being mounted perpendicular to a plane intersecting the path curve at onl three points and whose maximum displacement'from said curve is a minimum distance as compared to other'planes so intersecting said curve.

3. The combination with an irregularly curved windshield having a convex outer surface, of a 'vvin'd'shi'eld wiper assembly having a'drive :shaft axis and a wiper arm, saidwiper arm having an plane which plurally intersects said non-planar path curve and whose maximum displacement from said curve is a minimum distance as 'compared to other planes so intersecting said curve, said axis lying within a vertical plane perpendicularly related to said optimum plane, said axis also being obtusely disposed to said optimum plane and said convex outer windshield surface.

RAYMOND O. DO'SS.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Zierer Sept. 2, 1941 Paton Aug. 22, 1944 Sacchini May 15, 1945 Christel Oct. 23, 1945 Rappl June 11, 1946 

